Drafting-digitizing apparatus



Aug. 27, 1968 c. H. LITTLE ET Al. 3,398,452

DRAFTING-DIGI'TIZING APPARATUS 1O Sheets-Sheet 1 Original Filed March 4,1963 INVENTORS E 0 T. W S L m m Mu BKW mH 0 E N Lw R G A U HWE C ATTORNS Aug. 27, 1968 c, ET AL 3,398,452

DRAFTING-DIGITIZING APPARATUS l0 Sheets-Sheet 2 Original Filed March 4,63

all]

INVENTORS CHARLES HUBBARD LITTLE.

WALDO H. KLIEVER EU GENE L. W

gas,

W fi

. ATTORNEYS Aug. 27, 1968 c. H. LITTLE ET 3,398,452

DRAFTING-DIGITIZING APPARATUS 10 Sheets-Sheet 4 Original Filed March 4.1963 m I T S O RL T EE mw s VA L 1 W K N w R HH E SON EDE LLG V RAU WE 70 MN Q MN MN NM ON hm \N N v x H ww Aug. 27, 1968 c, H. LITTLE ET AL3,398,452

DRAFTING-DIGITIZING APPARATUS l0 Sheets-Sheet 5 Original Filed March 4,1963 ON kk u T M m RB WMWM S VMEE 9 N L I. J H H. L o S ON A Mm. A U.WEW C Aug. 27, 1968 c, ET AL 3,398,452

DRAFTING-DIGITIZING APPARATUS Original Filed March '4, 1963 10Sheets-Sheet e I 92 I I I I g pm 'hJLL i i,

' INVENTORS I95 I96 I97 19 /98 /8 CHARLES HUBBARD LITTLE I I WALDO H.KLIEVER I 5 LIE LS I A r f I ATTORNEY? Aug. 27, 1968 c, H, ET AL3,398,452

DRAFTING-DIGITIZING APPARATUS Original Filed March 4, 1963 10Sheets-Sheet 8 v r r I 1 I QO UO G U & |1- I I 6 TABLE POSITION *J --ATABLE POSITION 380 Y x ,2 *f, Y 3 376 souo fimsn 377 "C v 266 267 Manna.MIN. MAX- TABLE A TAPE TABLE B SPACE DASHUNE i TAPE 5' 27 an. .mnzx w 0I 370) .J 270 F2f7/ 27/ A B R2532! 111223] wTURRET 275 "Sn TAPE FWIR munin R? Resz'r R255! 385 386 3 '90 263 283 STYLUS- C OMMANO P015: S73E46!PULSE INPUT Z8 7 M ["1 PUISE ssemmvn v l8l I CHM/{AZ or4 Pik AXIS U 0 26 215 28 9 OR GATE I00 KC r0 DIFFERENT/AL 3) cowvrt'r? J PM OTHER P0185SEPARATOR 288 or 5.4M: Axis A00 29? INVENTORS SUWACT CONTROL egg/MT, ToOWE/Wm CHARLES HUBBARD LITTLE I6,667 PPJ 293 WALDO H. KLIEVER EUGENE L.WIEgELS FIG 20 momma/v0 I I l ATTORNEYS TRA usauczn United States PatentO 3,398,452 DRAFTING-DIGITIZING APPARATU Charles Hubbard Little,Cleveland, and Waldo H. Kliever and Eugene L. Wiemels, ClevelandHeights, Ohio, assignors to Universal Drafting Machine Corporation,Bedford Heights, Ohio, a corporation of Ohio Continuation of applicationSer. No. 262,590, Mar. 4,

1963. This application Mar. 2, 1966, Ser. No. 540,123

31 Claims. (Cl. 33-18) The present invention relates to drafting andlike apparatus.

This is a continuation of our application Ser. No. 262,- 590, filed Mar.4, 1963, now abandoned.

One of the principal objects of the invention is the provision of anovel and improved drafting machine or like apparatus capable of makingdrawings including con tinuous or dash straight lines, curves, circles,etc., mathematically generated designs such as loft lines, loftdrawings, templates, etc., and mirror-image or reverse drawings, etc.,using pencils, pens, scribe tools, etc., under the control of or inaccordance with information supplied from any source of absolute orincremental digital data, preferably any one of several commerciallyavailable contouring or positioning numerical control directors orsystems utilizing manual, punched cards, tape, either magnetic orpunched, etc., input media which can supply incremental X, Y, and Z andother axes command pulses and auxiliary command pulses or signals.

Another of the important objects of the invention is the provision of anapparatus which can be used for plotting a verification of producttapes, etc., intended to be used on numerically controlled productionmachines and the like and which can also follow a drawing, etc., andgive position data at a visual station or in automaticallytyped programor tape format.

Further objects and advantages of the invention will be apparent tothose skilled in the art to which it relates from the followingdescription of the preferred embodiment described with reference to theaccompanying drawings forming a part of this specification, in whichsimilar reference characters designate corresponding parts, and inwhich:

FIGURE 1 is a plan view of an automatic drafting machine forming a partof the preferred embodiment of the present invention; 1

FIGURE 2 is an elevational view, with portions broken away, of theapparatus shown in FIGURE 1, looking from the lower side of FIGURE 1;

FIGURE 3 is an elevational view of the apparatus shown in FIGURE 1,looking from the left side of FIG- URE 1;

FIGURE 4 is a view approximately on the line 4-4 of FIGURE 2;

FIGURE 5 is a view approximately on the line 5-5 of FIGURE 4;

FIGURE 6 is a view approximately on the line 6-6 of FIGURE 4;

FIGURE 7 is a view approximately on the line 7-7 of FIGURE 4; r

FIGURE 8 is an enlarged fragmentary sectional view approximately on theline 8-8 of FIGURE 1;

FIGURE 9 is an enlarged view of the lower left-hand portion of FIGURE 8;

3,398,452 Patented Aug. 27, 1968 FIGURE 10 is an enlarged fragmentarysectional view approximately on the line 1010 of FIGURE 9;

FIGURE 11 is an enlarged plan view with parts broken away and in sectionof a portion of FIGURE 1;

FIGURE 12 is an enlarged front elevational view of a portion of FIGURE11;

FIGURE 13 is an end elevational view looking from the left of FIGURE 12with portions in section approximately on line 13-13 of FIGURE 11;

FIGURE 14 is a fragmentary sectional view approximately on the line 1414of FIGURES 11 and 12, with portions in elevation;

FIGURE 15 is an enlarged sectional view of a portion of FIGURE 14 withportions in elevation;

FIGURE 16 is a fragmentary bottom view of a portion of the apparatusshown in FIGURE 11;

FIGURE 17 is a view approximately on the line 1717 of FIGURES 12 and 14,with parts shown in a different operating position;

FIGURE 18 is a fragmentary view of a control panel showing part of thecontrols employed;

FIGURE 19 is a block diagram of part of the electric control system;

FIGURES 20 and 21 are detailed schematic drawings of portions of FIGURE19.

The present invention comprises a power driven table apparatus andrelated equipment and a control apparatus which supplies motion andauxiliary function command impulses or signals to the table apparatusand its related equipment for actuating or controlling the movements ofthe table apparatus. The control apparatus which supplies the motion andauxiliary function command pulses or signals may utilize various inputmedia, such as manual control, magnetic or punched tape, p'unched cards,table signals, etc., which input is converted by data processing in thecontrol apparatus and the table apparatus and its related equipment intoaccurate movements of the table apparatus. The command signals for thetable apparatus and its related equipment may come from or be suppliedby any one of a variety of sources, such as a numerical controlcontinuous path or contouring control director, manually manipulatedoscillators and multipliers, and/ or computers. The output may be adrawing, or the like, or digital position data in decimal orbinary-coded decimal form at a visible station or in automatically typedprogram or tape format.

Referring to the drawings, the apparatus shown comprises a tableassembly K; two runway beams A-1 and A2, also referred to as the A-1 andA-2 beams, selcured to the table K, adjacent to its bottom and topedges, respectively, as the table is viewed in FIGURE 1; a first movableassembly including a third beam B, also referred to as the B-beam,having its opposite ends secured to carriages P and Q, supported by theA-1 and A-2 ,be'ams, respectively, for linear movement therealong,

from the control apparatus. The invention is illustrated as embodied inan apparatus from making drawings and the like, and the instrumentsshown are marking type stylus, but as previously suggested, othersuitable instru- Y ments may be attached to the carriage R.

In the subsequent description of the drafting apparatusshown, movementof the A assembly, including beam B and carriages P and Q, along beamsA1 and A2 and in turn movement of a stylus carried by the B assembly,including carriage R and stylus head S, from left to right and viceversa, as viewed in FIGURE 1, is referred to as movement in or along theA-axis in a plus or minus direction, plus being toward the right andminus toward the left. In like manner, movement of the B assembly,including carriage R and stylus head S along the B-beam and in turn astylus carried there-by toward the bottom and top beams A-1 and A-2, asmovement in or along the B-axis in a plus or minus direction, plus beingtoward beam A-2 and minus being toward beam A-l. Movement of the stylusin operative position into and out of engagement with the drawing paperL or other material to be worked upon and supported on table K, that is,in a direction normal to the top of the table is referred to as stylusdown and stylus up directions, down being movement of the stylus towardthe table and up being movement away from the table.

Movement of carriages P and Q along beams A-1 and A-2, that is, movementof the A assembly along the A- axis; movement of B assembly, that is,carriage R along beam B; and movement of the stylus in operativeposition into and out of working or marking position, that is, movementat right angles to the plane of the table top, as well as indexing ofthe stylus turret, etc., are under the control of the control apparatus.In the embodiment of the invention illustrated the control apparatus isa numerical continuous path or contour control director similar to thatemployed as a contouring control for machine tools and more particularlya TRW-300 control system or director produced by Thompson RamoWooldridge, Inc.

The control apparatus mentioned operates from a standard 1" punched tapeand supplies information to the drafting apparatus in the form ofappropriate incremental X and Y pulses for controlling movement of thestylus head along or in the. directions of the A and B table axes andadditional pulses or signals for performing auxiliary operations, suchas, down and up signals for controlling movement of the stylus in theoperating position toward and from the table top, and index pulses orsignals for indexing the stylus turret, etc. The table apparatus and itsrelated equipment accepts the command pulses or signals from the controlapparatus and converts them through appropriate data processing andservo apparatus into accurate movements of a stylus to produce drawingsand the like. In an inverse manner a stylus can be made to follow adrawing, etc., and the apparatus made to emit digital position data indecimal or binarycoded decimal form at a visual station or on a tape,etc.

The table K, shown, includes a fabricated prestressed aluminum table topM or work support provided with a flat linoleum surface to which adrawing material L or the like, to be marked, scribed or engraved, etc.,may be secured by tape or other conventional means. The table top M maybe supported in any position, for example, horizontal or vertical, byany appropriate means. The

top M is shown as supported in a horizontal position upon 'a pluralityof aluminum channel members or cross girders 3, 4, 5, 6 secured to asuitable sub table structure N including legs 7 fitted -with levelingadjustments and vibration absorbing pads. The sub-table N comprises arectangular frame 8, sometimes referred to as apron, formed of heavyaluminum angles reinforced at the corners by angle braces. The tableshown is slightly more than twice as long as it is wide and the tabletop M overhangs the sub-table N a small amount. The frame 8may bereinforced by one or more transverse channels 9 suitably connectedthereto as shown in FIGURE 7. Each of the long sides of the apron 8 isprovided with an extruded aluminum truss bar 10, the cross-sectionalshape of which is rectangular. The tops of the truss bars are spaced ashort distance below the inwardly projecting top flanges of the apronand are substantially as long as the sideof the apron which they adjoin.The. ends of the truss bars are connected to the vertical flange of theapron adjacent thereto by bolts 11 extending through aligned holes inthe bars and apron and in which they engage, preferably without unduelooseness. A plurality of similar bolts are spaced intermediate the endbolts, but the holes in the apron through which these bolts extend areslightly elongated vertically.

The table top M is placed upon the apron 8 of the subtable with thegirders 3-6 resting upon the top of the long sides of the apron 8 andbolted to the top flange thereof by bolts 12 having round heads locatedat the underside of the top flange of the apron and spaced above theunderlying truss bar. Lock washers may be interposed on the boltsbetween the underside of the girders and the top of the apron and/orunderneath the heads or nuts. The two longitudinally extending trussbars are connected by extruded aluminum tie bars 13, also rectangular incross section and connected to angles by suitable recess headed screws,which angles are in turn connected to the truss bars by similar screws.One of the tie bars 13 is located underneath each of the two girders 4and 5 or the table top M.

The truss and tie bars 10 and 13 are provided with vertically extendingrecess headed bolts or jackscrews 14 used for leveling the table top M.Each screw 14 extends vertically through the bar in which it issupported and is provided at its upper end with a nut which can be usedto raise or lower the screw in its respective bar. The upper ends of thejackscrews 14 abut the head of one of the bolts 12, previously referredto. Since the tie bars 13 are shown only about half as deep as the trussbars 10, tubular spacers are interposed between the top walls of the tiebars and the nuts of the jackscrews or bolts carried thereto. With thetable top M bolted to the subtable N and the bolts 11 slightly loosenedso that relative movement can take place between the parts of the apron8 and the truss bars 10 between the end bolts 11, the jackscrews 14 maybe rotated relative to their nuts to naise and lower the upper endsthereof and thus level the work surface of the table top M and the bolts11 thereafter tightened. The construction just described provides arelatively light table structure requiring merely four legs, but the topworking surface of which can be made and maintained level. In thepresent instance the top 4 is provided with an all aluminum vacuum chuck15 placed thereon and having paper engaging and locating fixed cornerstops 16, 17 on the lower right-hand corner of the chuck and anadjustable stop 18 attached to its lower right-hand edge. As will beunderstood, the drafting paper L, shown on the chuck 15 may be moved orpositioned by the adjustable "siop 18 to orient a drawing thereon in theplane of the t-rackways on beams B, A-1 and A-2 along which the A and Bassemblies move.

The vacuum chuck 15, shown, comprises a cast aluminum sub-base havingair grooves milled therein in the form of a grid and a cover plate orsheet of anodized aluminum which serves to provide the drawing or workreceiving surface. The ends of the grooves in the sub-base are closedand the grooves are connected to a suitable vacuum pump not shown. Thecover sheet has a plurality of small holes drilled therein and whichcommunicate with the grooves milled in the sub-base. In the embodimentshown, the holes are spaced on 1 /2" centers and have a diameter of.025". The chuck is adapted to hold drawings smaller than the areaprovided with holes by using masks to mask off or close the holes notcovered by the drawing. A vacuum actuated circuit control is providedfor stopping the operation of the apparatus if the vacuum fails.

The accuracy of the drafting apparatus is largely dependent upon thestraightness and alignment of beams A1, A2 and B and the accuracy withwhich carriages P, Q and R are moved therealong. Since the beams arealike and since the carriages are connected to the respective beams uponwhich they are supported in like manner only the A2 beam and the mannerin which the carriage Q is connected thereto will be described indetail. The corresponding parts of beams A1 and B and carriages P and Rwill be designated by the same reference characters with prime anddouble prime marks affixed thereto, respectively.

Beam A2 is a hollow tubular aluminum extrusion 20 which providesrigidity in both bending and torsion modes and has an integralstiffening cross rib 21 in a plane parallel with the plane of theworking surface of the table top, beams A1 and A,2 are secured to thetable K by a plurality of longitudinally spaced brackets 22, 23,respectively, detachably bolted to opposite ends of the channel members3 to 6 at the sides of table top along which they extend and to planarribs 25, 25 along the left and right hand side of the beams A2 and A-1as they are viewed in FIGS. 3 and 8. The brackets 22, 23 and the outersides of the beams A1 and A2 are protected by movable covers 26, 27,respectively, suitably connected to the table. Oppositely facing V-ways32 and 33 are precision machined on the upper and lower side of beam A2directly above and below the right hand side 34 of the beam as viewed inFIG. 9. The side 34 of the beam is planar and has a precision rack 35thereon formed by a plurality of aligned short rack sections detachablybolted thereto.

The V-ways on beams A-1 and A2 form trackways or guideways for carriagesP and Q to which the ends of the B-beam are connected. The carriage Q issupported on the beam A2 by four ball bearing rollers 40, 41, 42, and 43having hour-glass shaped treads for engagement with the V-ways on thebeam and adjustably connected to the carriage Q so that they can be setto snugly fit the ways. Carriages P and R, as previously stated, aresupported on the respective beams A-1 and B along which they travel insimilar manners and the corresponding parts are designated by the samereference characters having prime and double prime marks appliedthereto, respectively. The carriages are aluminum castings designed forrigidity and light weight and the opposite ends 'of the B-beam areconnected to the carriages P and Q, so as to provide adjustment formechanical squareness while al-' lowing a little freedom to avoidstress.

Carriages P, Q and R are moved along their respetive beams Al, A2 and Bby servo motors 45, 46 and 47, respectively, which in the presentinstance are 400 cycle 2 phase alternating current motors. The motorsare provided with 400 cycle tachometer generators 48, 49 and 50 (seeFIG. 19) for stabilization purposes and are connected to the precisionracks 35', 35' and 35" by suitable gearing including precision pinions51, 51 and 51", respectively, in mesh with the upper portions of theracks. Carriages P and R are also provided with digital incrementaltransducers 52 and 53, respectively, also connected to the racks 35' and35", by gearing ineluding precision pinions 54 and 55 in mesh with thelower parts of the racks 35 and 35", respectively. The

racks have relatively wide faces and the fact that the pinions connectedto the drive motors engage the upper parts of the racks while thepinions connected to the transducers engage the lower parts thereofprevents any wear occurring as a result of the power drive from beingreflected in the measuring or feedback mechanism. Carriage P is furtherprovided with a synchro transmitter 56 geared to rack 35' and carriage Qwith a synchro control transformer 57 geared to rack 35, and which areutilized to maintain constant working coordination between the twocarriages P and Q, both of which carriages receive their basic drivesignals from the same command. Carriage R is further provided with amechanical inertia balancer 60 which compensates for the difference inweight between the movable A and B assemblies. The inertia balancer 60,shown, comprises a cylindrical flywheel of suitable weight connected tothe rack 35" of beam E by gearing including a pinion 61 engaging theupper part of the rack 35". When the carriage R is moved back and forthalong the B-beam the flywheel rotates and provides an inertia balanceserving to compensate and make the moments of inertia of the B assemblyequal to or look like the moments of inertia of the movable A assembly.The left-hand end of beams A-1 and A2 are provided with adjustable stops62 and 63 for limiting movement of carriages P and Q toward the left, asviewed in FIG. 1, and beam B is provided with a similar stop 64 forlimiting movement of carriage R toward beam Al, the table or board zerobeing adjacent to the lower left-hand corner of the table. Beams A1 andB are provided with microswitches 65 and 66 actuated by suitable strips67 and 68, on carriages P and R, respectively, as the carriages approachthe stops 62 and 64.

The electrical transmission between the stationary part of the controlcircuitry, most of which is housed in a control console, and the movableA and B assemblies is by a plurality of spring sliding contacts 70, seeFIGS. 8, 9 and 10, carried by brackets 71, 72 and 73 on the movablecarriages P, Q and R and slidably engaging conductors 74 carried by thebeams A1, A2 and B, respec tively. The conductors 74 on the beams arepositioned in grooves in extruded plastic strips 75, 76 and 77 havingdove-tail connections with undercut pads on the undersides of beams Al,A2 and B, respectively. Each circuit includes four parallel connectedsliding contacts. The sliding contacts or brushes and the conductorswith which they engage are made of or laminated with noble metal and areunderneath the beams where they are out of the way and protected againstdamage.

As previously indicated, the preferred embodiment of the inventionincludes stylus head S, comprising an indexible turret T provided with aplurality of styli. It is, however, to be understood that this head isinterchangeable on carriage R with any other suitable mechanism.

Referring particularly to FIGS. 11-17, the stylus head shown comprises afabricated frame 80 connected to carriage R for movement toward and fromthe plane of the table K by cap screws 81, 82, 83 and 84 projectingthrough elongated slots in frame 80 and threaded into suitable tappedapertures in carriage R. The cap screws have enlarged washersimmediately underneath their heads and saucer-like resilient orBellville washers therebetween and the surface of the frame 80. The capscrews are tightened sufficiently to cause the washers to resilientlyhold frame 80 against carriage R so that it can be readily adjusted totake care .of directing of scribing material of different thickness,etc. toward and from the plane of table A upon manual rotation of anadjusting screw 85 threaded into a tapped aperture in frame 80 andhaving its lower end rotatably connected to a forwardly extendingprojection 86 on a member 87 secured to carriage R. Frame 80 has avertical slot 90 therein through which extension 86 of member 87projects and a groove 91 into which a part of member 87 engages andwhich together with a member 92 secured to carriage R below member 87and projecting into the same slot 91 keys and guides the stylus head asit is adjusted toward or from the working surface of table K.

Stylus head S, as previously stated, includes an indexible turret Tcomprising a generally cylindrical member 95, supported in bracketassemblies 96, 97, forming parts of frame 80, for rotation about an axisnormal to the drawing surface of table K on a shaft or pin 101 by a pairof spaced anti-friction bearings 102, 103. Pin 101 is fixed in thebracket 97 and a member 105 connected to bracket 96. Turret member 95,as shown, is provided with a plurality, in the present instance, sixcylindrical apertures parallel with its axis of rotation and within eachof which is secured a pair of upper and lower bushing members,designated 105, 106, and 105' and 106', in FIGS. 14 and 15, for slidablysupporting suitable styli 107 to 112. Turret T also includes an invertedcup-shaped cover member 113 connected to its upper end and havingapertures therein through which the styli may be inserted and removedand through which the upper ends of the styli project. The turret alsoincludes a plurality of light springs, designated 114 and 114 in FIGS.14 and 15, each interposed between one of the upper stylus supportingbushings and a flanged washer-like member, designated 115 and 115normally engaging the underside of turret cover 113. Each flangedwasher-like member has a boss, similar to boss designated 116 in FIG.15, projecting upwardly through turret cover 113. The particularconstruction of one of the various styli that may be used, that is,stylus 110, is shown in considerable detail in FIG. 15. Stylus 110,shown in FIG. 15 is utilized to make ink lines on a drawing and, forpurposes of illustration, is a duplicate of stylus 107.

The two styli 107, 110, are shown in operating and inoperating stations,respectively, and the corresponding parts are designated by likereference characters with prime marks affixed to those applied to stylus107. Stylus 110 includes a cylindrical tubular body 117 slidablyreceived in the pairs of aligned stylus supporting upper and lowerbushing members 106, 105, fixed in the turret member 95.

Stylus body 117 has an inking assembly, designated generally as 118,detachably threaded, in its lower end. It is to be understood, however,that any suitable marking, scribing .or engraving device or tool may besubstituted for the inking assembly 118 shown. The upper end of thestylus body 117 has a tubular member 120 detachably fixed thereto as bybeing threaded thereon, the intermediate portion of which is providedwith a plurality of threads upon which a member 121 is threaded. Member121 has an external annular flange adjacent to its upper end adapted tooverlie and engage an oppositely facing internal annular flange adjacentthe lower inside edge of an inverted cup-shaped or cap member 122.Member 120 is tubular, projects above member 121 and cap 122 has acylindrical projection extending into the upper end of the opening inthe member 120 which guides the cap member as it is moved relative tomembers 120 and 121. Cap member 122 is urged in an upward direction, asviewed in FIG. 15, to engage the annular flanges, referred to, by aspring 123 interposed between the upper end of member 121 and the insideof cap 122. Spring 123 surrounds the upper end of member 120 and thecylindrical downwardly projecting boss on the inside of cap 122. Thelower edge of cap member 122 engages the upper edge of flange 116 on thewasher-like member 115 and the lower edge of member 121 engages theupper side of washer member 115 inside of flange 116. It is recognizedthat it is difficult to have both of the aforementioned surfaces incontact with one another and it is immaterial which of the two surfacescontact.

From the foregoing description, it is believed that it will be apparentthat stylus 110 including 'body member 117, tubular members 120 and 121,cap member 122 and spring 123 can be removed and inserted bodily intothe turret T. This facilitates the supplying of the turret with anyparticular desired type of stylus.

It is further believed that it will also be apparent that the workingend of the stylus, designated 125, can be moved into engagement with thepaper or other article to be marked on the table therebeneath bydepressing the cap member 122. As the cap member is depressed the stylusassembly 110, and the washer-like member move downwardly against theaction of the light spring 114. When the point 125 of the stylus meetsresistance by its engagement with the article to be marked on the tabletherebelow, continued pressure on the cap 122 moves Washer 115 and cap122 downwardly relative to the stylus proper including body 117 andmembers 120 and 121 and the other parts of the stylus fixedly connectedthereto and the point of the stylus is pressed against the article to bemarked through action of spring 123. The strength of this spring 123 canbe made to fit any particular marking device in the stylus body 117 orforming a part of the stylus. Obviously, a heavier spring is requiredfor scribing a metal part than applying an ink mark to drafting paper.

The operating position for the styli carried by the dexible stylusturret 95 is the right-hand position, viewed in FIGS. 1 and 14 and thenear position, viewed in FIGS. 3 and 11.

The stylus in this position is moved into and out of contact with theworking surface therebelow by a ball bearing supported roller on aprojecting crank 131 on the end of a shaft 132 rotatably supported inthe frame 80 by spaced anti-friction bearings 133, 134. The bearing 133is carried by the member 104 of the frame 70 and the bearing 134 by amember 135 fixed to the bracket 96. The projecting end of the shaft 132upon which the roller 130 is supported is such that as the turret T isindexed to move a stylus into the operating position or station theupper end of the stylus is depressed as indicated in FIG. 14 by theroller 130 to move the working end of the stylus about half the distancewhich it must travel to move from rest position shown at the left sideof FIG. 1 to working position in engagement with the Work on the table.The shaft 132 is subsequently oscillated about its axis of rotation tocause the roller 130 to move the working end of the stylus into and outof contact with the drawing surface, etc. therebelow. The end of theshaft 132 opposite that to which the roller 130 is connected has a crankarm fixedly secured thereto, the projecting end of which crank arm isconnected by a pin 141 to a link 142 extending towards the right, asviewed in FIGS. 11 and 12, and connected at its opposite end by a pin143 to an arm 144 secured to a rotatable shaft 145 of an oscillatingsolenoid 146 carried by a bracket 147 forming part of the frame 80. Theshaft 145 projects through the solenoid 146 and the forwardly projectingend, as viewed in FIGS. 11 and 12 is provided with a knurled knob 148for manual oscillation of the shaft 145 and in turn reciprocation of thestylus in the working station on position.

From the foregoing it will be apparent that the stylus in the operatingor working station can be moved into and out of contact with the drawingsurface underneath either by manipulaton of the knob 148 or byenergizing and deenergizing of the solenoid 146.

The stylus turret T is indexed in steps of 60 to move the styli carriedthereby sequentially into the working station or position. In theembodiment shown, the turret is rotated clockwise, as viewed in FIGS. 11and 17, and the indexing is effected by the engagement of an indexingpawl with ratchet teeth formed on the periphery of the turret body 95.In the present instance there are six ratchet teeth 161166 correspondingwith the six styli 107-112 carried by the turret. When in any indexedposition the turret is accurately located and held thereon by theengagement of two members or lever arms 170, 171 with opposite sides ofthe lower bushing member in the operating station corresponding to thebushings 105 and 105', previously referred to and within which bushingthe particular stylus in the working station is carried. The lever 170is pivotally connected -by a pin 172 fixed to the frame 80 of the stylushead S for rotation about an axis parallel with the axis of rotation ofthe turret T and at the right of the stylus in the operating station, asshown in FIG. 11. The lever 170 is biased by a spring 173 connectedthereto and to the rear wall of the frame of the stylus head. The end175 of the lever 170, which end engages the periphery of the lowerstylus bushing is ground to a shape with respect to the pivotal axis ofthe lever such that as the spring 173 pulls it in a clockwise directionit functions as a cam surface to urge or hold the opposite side of theperiphery of the stylus bushing against the end 178 of the lever 171.

The lever 171 which engages the side of the lower stylus bushing in theoperating station opposite to that engaged by the lever 170 is one arm.of a bell crank-type lever mechanism 180 pivotally connected by a shaft181 carried by the frame of the stylus head for oscillation about anaxis parallel to the axis of the stylus turret and at the side of thestylus in the working station opposite to the axis of the lever 170. Thelever 171 is biased by a spring 182 in a counterclockwise direction, asviewed in FIGS. 11 and 16, and the end 178 thereof which en= gages thestylus bushing in the operating station is formed preferably 'bygrinding to a radius about its axis of rotation tangent to the stylusbushing when the stylus carried thereby is in the exact desired indexedposition. The spring 182 is connected to the lever 171 and to the rearwall of the frame of the stylus head.

The bell crank lever assembly 180 includes a second lever arm 190. Theindex pawl 160, previously referred to, and which engages the ratchetteeth 161-166 on the periphery of the stylus turret body member 95, ispivotally connected by a pin 191 to the lever 190 adjacent to its freeend. The pawl 160 is biased into engagement with the periphery of thestylus turret member 95 by a spring 192 connected thereto and to thelever arm 190. The bell crank lever 180, which is biased by the spring182 in a counterclockwise direction, is normally in the position shownin FIG. 12, and is moved in a clockwise direction to move its arm 171free of the stylus bushing in the operating station and to cause thepawl 160 to engage the proper ratchet tooth of the stylus turret andindex the turret 60 by a roller 195 carried on a pin 196 in the free endof a lever 197 fixed to the lower end of the rotor shaft 198 of a rotarysolenoid 200. As the lever 197 is rotated either by energization of thesolenoid 200 or by manual movement of a knurled hand grasp or knob 201connected to the upper end of the shaft 198, in a clockwise direction,the roller 195 engages a cam-like surface 202 on the left-hand side ofthe lever 190, .as viewed in FIGS. 11 and 17.

When the lever 197 has completed its clockwise rotary movement the partsare approximately in the positions shown in FIG. 17 with an abutmentsurface 205 on a projection 206 of lever 190 in engagement with one ofthe surfaces forming the ratchet teeth on the turret, such as, thesurface 207. This limits movement of the indexing mechanism includingindex pawl 160 and levers 190 and 196, etc., in the indexing direction.When the solenoid 200 is deenergized or the knob 201 released, as thecase may be, the pawl 160, levers 171, 190 and 196 are returned to theirnormal positions, that is, the positions shown in FIG. 11 under theaction of the spring 182. As the lever 171 is rotated counterclockwisefrom the position shown in FIG. 17 to the position shown in FIG. 11 itmoves into engagement with the bottom bushing of the stylus just movedfrom the operating station and pulls the turret around with it until thelower bushing for the stylus being indexed into the operating stationabuts against its end 178. This completed the indexing movement of thestylus turret. In other words, the free end of lever 171 comes to restagainst the stylus bushings in the operating station and the nextsucceeding station and the engagement of the lever 171 with the twobushings, referred to, limits movement of the indexing mechanismincluding the levers 171, 190 in a counterclockwise direction andpositions the turret. As the stylus being indexed into the operatingstation moves therein it moves down slightly, as previously mentioned,and as the lower stylus bushing clears the end of lever it drops inbehind the stylus bushing and wedges it against the surface 178 on lever171.

The control works on the closed-loop principle and the control apparatusemits a plurality of series of incremental electrical common pulses forcontrolling movement of the A and B assemblies, each having a value of.001" movement for the movable assembly which it controls. Since thereare only two movable assemblies A and B in the apparatus illustrated,only two series of impulses, that is, plus and minus X-axis impulses andplus and minus Y-axis impulses are required to operate the apparatus. Itis to be understood that other commands, for example, Z-axis and rotarymotions, etc. pulses can also be coded into the tape, if desired. Twocommand pulse channels are provided for each motion, one for producingmotion in the plus or positive direction and the other in the minus ornegative direction. Similar feedback pulses also having a value of orthe equivalency of .001" of movement are produced by the transducers 52,53.

Referring to FIG. 19, the plus X command pulses for the table A assemblyare delivered by the director to terminal 250 and minus X command pulsestherefor to terminal 251; the plus pulses for the table B assembly toterminal 250' and minus pulses therefor to terminal 251'. In addition,plus and minus pulses are available at terminals 255, 256, 255 and 256for jog operation of the A and B assemblies. Auxiliary function down andup signal pulses are delivered by the control apparatus to terminals 260and 261 for controlling energization of solenoid 146 for lowering thestylus in the operating station into and out of engagement with the workto be marked; on and off signal pulses for causing the stylus to producedash lines are delivered to the terminals 262 and 263; and an in-dexfsignal pulse for controlling energization of solenoid 200 for indexingthe stylus turret T to terminal 264.

In the preferred embodiment shown, the control apparatus is capable ofproducing X, Y and Z control or tape axis commands and either of thesecommands may be connected by tape axis selector switches 266, 267, seeFIG. 18, to either table A or table B movable assemblies.

From terminals 250, 251 the plus and minus control apparatus commandpulses are transmitted or fed to a manually operable three-position modeselector switch or control 270. The plus and minus jog pulses are alsotransmitted to the mode selector switch 270 by way of manually operatedplus and minus jog and step switch controls 275, 276. When the modeselector switch 270 is in one position, sometimes hereafter referred toas its normal position, the command pulses are transmitted to a manuallyoperable zero offset switch or control 271; when in a second position,the zero offset control 271 is connected to the jog and step push buttonswitch controls 275, 276, and jog pulses may be fed from the terminals255, 256 to the zero offset control 271 by manual operation of pushbutton switch controls 275, 276; and when in a third position, steppulses may be transmitted to the zero offset control by manual operationof switch controls 275, 276. A single pulse is fed to the zero offsetcontrol upon each actuation of either of the push button controlswitches 275, 276 when the mode selector switch 270 is in jog positionand a series of pulses when the mode selector switch is in stepposition. While the two mode selector switches 270 and 271' are shown asdiscrete controls, this is done for purposes of illustration, as bothselectors are preferably connected to a single shaft and operated fromone position to the other by a single manually engage-able knob.

The zero offset control 271 is a manually operable selecting switchwhich is normally set so that the pulse or minus impulses deliveredthereto continue onto a pulse separator 280, but which can be set in asecond position to deliver the pulses to an add-subtract counter 281,connected to a stylus table A-axis position indicator or readout 282.The counter is provided with a push button reset control 283.

The plus or minus command pulses coming from the zero offset control271, when in its normal and operating position, are transmitted to thepulse separator 280, as previously stated, along with plus or minusA-axis pulses from transducer 52. The function of the pulse separator isto separate in time the pulses from the command source and from thetransducer 52 so that even those coming simultaneously will be separatedin time as they are transmitted from the pulse separator to adifferential counter 285.

The operation of the separator is illustrated in the schematic diagram,FIG. 20. Each command pulse is stored in a storage fiip-fiop, therebeing such a flip-flop for each of the four pulse sources, that is,command plus and minus and transducer plus and minus. Only the pluscommand input terminal or source 286 and the storage flip-flop 287,therefore, are shown in FIG. 20. A scanner 288, operating at a ratecontrolled by a crystal clock 289, operates like a commutator tointerrogate or pulse the storage flip-flops successively. Pulses storedin the storage flip-flops are emitted through channel 291, therespective four channels or gates 290 connected therewith at intervalscontrolled by the interrogating pulse. The scanner also provides forswitching the differential counter between add and subtract modes bysupplying pulses from additional add and subtract control terminals orleads 292, 293, as shown in FIG. 20. For the scanner function, any of anumber of shift register or counter tube techniques may be applied. Inthe preferred embodiment, a ring of flip-flops is stepped by the crystalclock to feed pulses successively into the output lines.

To prevent interference in cases where the command pulse and theinterrogating pulse come into the separator channel simultaneously anand not gate 294 allows the command pulse full authority during a periodof time of ten microseconds due to the action of one shot flip-flopdelay units 295, 296.

If the interrogate pulse is inhibited because of a simultaneous commandpulse in the same channel, the timing is designed so that anotherinterrogation pulse will remove the pulse from storage before anothercommand pulse can occur in that channel. It will be recognized by thoseskilled in the art that other storage devices, for example, a magneticcore and other types of delay devices could replace those referred to.

The differential counter 285 computes a binary number which at eachinstant represents the difference between the pulses received from thecommand and those received from the transducer. In the preferredembodiment transsistor flip-flops are used although other types ofcounters, such as magnetic cores, tube flip-flops or counter tubes wouldbe applicable. When the scanner passes the line or terminal 292, markedadd control, the counter is switched so that pulses coming in willincrease its count. This is accomplished by the control of carry gatesso that any flip-flop returning from the set to the reset or zeroposition will produce a carry pulse to the next stage. The add controlpulse from the scanner switches the add-subtract control flip-flop 297,which in turn holds the carry gates in the add mode until a subtractcommand is given later in the cycle. The counter will next receive aplus command pulse and a pulse from the transducer, which latter pulsemust be negative, in order that the counter can produce the difference.The scanner will 12 next provide a subtract control pulse followed bypulses from the command and transducer if such pulses have been storedsubsequent to the last interrogation.

There are provisions in the counter for introducing pulses over channels300 and 301 which set the counter to zero for test purposes or providean 88 bit command for zero return to be described later.

Since the servo motors 45, 46 for the A assembly are two-phase motorsoperating from 400 cycle alternating current supply, the number storeddigitally in the differential counter 285 must be converted in amodulator 305 to a 400 cycle voltage which is proportional to the digitnumber. The counter shown has a chain of seven binary flip-flops and themodulator is so designed that it provides a zero output when the counterreads 127. As the counter moves from 127 toward its zero the 400 cyclewill decrease in value and have a given phase and if the counter movesfrom a 128 to 225, the 400 cycle will be of increasing value. The 400cycle control signal at 3.15 volt is introduced at terminal 306 alongwith a plus 10 volt direct current which maintains the instantaneousvoltage always positive. This is switched into the respective summingresistors 307-315 by summing gates 316-322 controlled from thedifferential counter flip-flops. The summing resistors are weighted sothat the smallest or unit number passes through a high resistance of128,000 ohms while the most significant or highest number passes througha low resistance of 1000 ohms. Thus when any flip-flop is in its setposition it produces a current in the summing channel or point 323corresponding to the value of the number which that flip-floprepresents. The summing resistors feed into a feedback operationalamplifier according to principle well known in the analog computer art.

In order to eliminate steps in the direct current input to the amplifierwhen the flip-flops change, the reset position of the flip-flops alsooperates gates 325-332 into summing resistors 335-342, but the gatesswitch only a plus 10 volt direct current value from source or terminal345 without the 400 cycle component.

In order to provide zero 400 cycle output when the counter is at areading of 127, a 400 cycle source 346 of opposite phase to that used onthe gates is permanently connected into the summing point through aresistor 347 which is shown adjustable. The direct current component inthe summing point is eliminated by an additional minus 10 volt directcurrent source 348 through an adjustable Summing resistor 350.

With this modulator a 400 cycle output is provided at the outputterminal, which varies in amplitude and sign according to the digitalsetting of the differential counter.

The 400 cycle alternating current voltage from the modulator 305 istransmitted through line or channel 350 to preamplifiers 360, 361 andpower amplifiers 362, 363 of the respective servos 45, 46 which drivethe two ends of the movable A assembly. The inputs through thepreamplifiers also receive signals from the respective tachometers 48,49 and the preamplifier 361 from the syn chro control transformer 57. Aninput for quadrature compensation signals is also provided which correctquadrature noise signals at zero from the tachometer, controltransformer and other devices. In any specific preamplifiers the various400 cycle inputs are summed through summing resistors into a feedbackoperational type amplifier. They are then shifted in phase by and afterfurther amplification are applied to the amplifier phases of the 400cycle servomotors 45, 46.

In the case of the two A assembly servos 45, 46, each of them receivesthe main signal controlled by the modulator 305. The purpose of the twosynchros 56, 57 is the coordination of the motions of the two servos 45,46 by producing a corrective signal for servo 57 which causes it toadvance or retard, if necessary, to maintain the B beam perpendicular tothe A-1 and A-2 beams.

The control for the B servo motor 47 is the same as FIGS. 18 and 19 are,however, identified by the same reference characters as used indescribing the A assembly control, but with a prime mark affixedthereto.

It will be understood, however, that as an alternative construction thesynchros 56, 57 could 'be omtted and the carriage Q provided with atransducer and its movement controlled in a manner similar to that inwhich the movement of the carriage P is controlled As previously statedthe tape may have coded therein two or three axes information, forexample, X and Y axis information or X, Y and Z axis information and thetwo switches 266 and 267 on the control panel are provided for selectingwhich axis of tape information is used in the A-axis of the table andwhich in the B-axis f the table. The switches make it possible to selectany view of the workpiece being drawn or to successively draw severalviews in different desired positions. The drafting machine can beprovided with a rotating table section and the tape provided withrotational axes information, if desired. The switches 266 and 267provide signals which control gating circuits in the director. By thismethod the need for unnecessary long leads carrying signals isobliterated thereby reducing problems of stray noise.

The control apparatus also comprises switching means for reversing thesign of the signals or impulses being fed into either the A or B axes ofthe table. This reversal takes place within the control apparatus whichalso provides sign reverse signals or pulses for the sign reversecontrol 365 and 365' which reverse the transducer signals or pulses tothe readouts. The sign reverse signals or pulses for reversing the signsof the transducer pulses or signals also provides plus or minus signs onthe readouts to be described.

It is important to many applications of the apparatus that there beprovided as a reference a point on the table which is absolute A-axiszero and B-axis zero. This point is mechanically determined so that ifthrough loss of power or for other reasons the flow of data to thecounters is interrupted, it will be possible to reestablish any positionon the table or drawing. This zero-zero point is reached by depressing azero return button 370, shown on the panel, FIG. 18. When this button isdepressed, by appropriate relay switches and time delay circuitry, the400 cycle signal from the A and B modulators 305, 305' are disconnectedand a 400 cycle signal is provided to the servo amplifiers for both theA and B table axes to cause both the A servos 45, 46 and the B servo 47to move the movable A and B assemblies toward the A-axis zero and theB-axis zero. As the A and B assemblies approach the mechanical stops 62and 63, trips 67 and 68 carried thereby actuate zero approach switches65, 66 on beams A-1 and B. These switches reduce the 400 cycle input tothe servo motors to slow down the movable A and B assemblies so thatthey approach the mechanical stops slowly. The actuation of the zeroapproach switches 65, 66 also starts time delay-devices 371 and 371which allow ample time for the movable assemblies to arrive at theirmechanical stops and be held there with sufficient pressure to insurefixed positions. When the time delay expires, numbers 88 are preset intoeach of the differential counters 285 and 285' and the zero returnbutton is released. The release of zero return button returns themodulator signals to servo control. The servos will then move assembliesA and B. .088" from the mechanical stop thereby reducing the signal inthe differential counter to zero. This position is defined table A and Bzero or merely as table zero.

If differences larger than 128 bits are introduced into the differentialcounters they will reverse their drive signal and subsequent data willhave no value. This is an abnormal condition and protection is providedby out of synchronism controls 372 and 372' which cause signals to beemitted to the control apparatus to stop the pulse trains, if for anyreason the signals in either differential counter becomes larger than 96bits. The out of synchronism detectors 3'72 and 372', shown in FIG. 19,monitor the differential counter outputs.

The stylus is caused to make contact with the paper by energization ofsolenoid 146, as already indicated. This is controlled by relays withholding circuits. A signal from the tape coming through the controlapparatus to terminal 260 and calling for stylus down will operate relayand holding circuits which will hold or maintain the solenoid 146energized after the short pulse from the control apparatus is no longeractive. When a pulse from terminal 261 is produced by appropriate tapecoding, the holding circuit is broken by another relay so that thesolenoid releases the stylus. The relays can also be operated by amanual stylus control to remain in either the up or down position.

A dash line generator 376, also controlled from the stylus control 375,provides for interrupting the circuit to solenoid 146 so that it isintermittently caused to go up and down thereby making a dash line. Thedash line generator 376 is basically a free-running multivibrator andthe length of lines and the space between lines are independentlyvariable by line and space controls 377 and 378 on the dash-line sectionof the control panel. The on time for one of the transistors of themultivibrator is controlled by the size of a capacitor and a rheostatwhich control the feedback. Likewise the on time of the other transistorof the multivibrator is controlled by another capacitor and rheostat. Byconnecting the output of one transistor into an appropriate poweramplifier to operate the solenoid 146, the stylus will be in the downposition for one state of the multivibrator and in the up position forthe other state of the multivibrator. The one rheostat, therefore, willcontrol the length of time that the stylus is down and, in turn, thelength of the line or dash produced. This rheostat is operated by theline length control 3-77. Likewise, the other rheostat, operated bycontrol 378, controls the up time of the stylus and, therefore, thelength of space between the lines. The manual override control switch380', on the dash-line control section of the control panel, makes itpossible to select dash lines manually or to insure a continuous solidline which the tape cannot alter.

The drafting apparatus, as previously described, may or may not beprovided with a rotary turret provided with different pens or otherscribing styli or other tools. The preferred embodiment shown anddescribed has such a turret T advanced always in the same direction by astep equal to the space between the tools. This step is produced byenergization of the rotary solenoid 200, already indicated, upon thereception of a single input pulse from the control apparatus by way ofterminal 264 as a result of instruction coded in the tape. Indexing ofthe turret T may also be effected by the depressing of turret index pushbutton 381 on the control panel. The indexing of the turret may beplaced under control of the control apparatus or the turret index switchor disconnected from all sources of signals and the possibility ofturret advance thus prevented by a turret control selector switch 383 onthe control panel. When a pulse is introduced into the control circuitfor indexing the turret T, a monostable flip-flop unit maintains anoutput signal of sufiicient time duration to insure a full stroke ofsolenoid 200.

The purpose of the tachometers 48, 49 and 50 in the servo system is tostabilize the system against overshooting or hunting. In the case of thedrafting apparatus, sufficient dampening from the tachometers isnormally introduced so that if, at any time, a command signal issuddenly interrupted the stylus will not overshoot the position calledfor. There will be some rounding of corners if the command direction issuddenly changed and the control system, either with or withoutinstruction from the tape, is made to anticipate sharp corners and withthe tachometer the command is made slower or interrupted to allow timefor the stylus to reach the corner before a command for a new directionis introduced. If the application requires only modest accuracy, suchprecaution may be omitted.

The control shown for the automatic drafting apparatus includes twoindicators or readouts 282, 282' which give the table position of thestylus in terms of the position of the A and B movable assemblies. Thesenormally read achieved motion of the respective movable assemblies byaccumulating pulses from the A and B transducers 52, 53. The accumulatednumber normally starts with zero for the zero table position, but otherzeroes may be set, as will presently be described. In principle, eachindicator shows the position of a decim'al add and subtract counter.When a transducer plus pulse comes on the plus A or plus B lead, itoperates a flip-flop to switch the counter to the add mode position. Thepulse is delayed to allow time for a flip-flop to introduce the addcontrol into the carry gates after which the pulse is added. A similaroperation takes place for a transducer negative pulse on the negativeleads except that the add subtract control flip-flop is placed in thesubtract mode.

For some applications it is desired that the position indicator startfrom a zero at some other place on the table than the defined tablezero-zero, or that it operate with respect to a point off the table. Forthis purpose the counters and indicators can be disconnected from theservo controls and pulses introduced therein by depressing the zerooffset push buttons 271 and 271, shown on the control panel. Such pulsesmay originate from the jog control switches or the step controlledswitches or, if desired, from tape readings. In the normal use of thisfeature, the stylus is returned to its zero-zero table posi tion beforethe desired plus or minus offset is introduced.

The indicators 282, 282' also provide for indicating which tape axisinformation has been selected by controls 266 and 267 for the table Aand B axis and for indicating whether a sign reversal has been calledfor.

A push button switch 385 on the control panel is provided for startingand stopping the vacuum pump connected to the vacuum chuck 15 whichholds the medium to be marked on the table. This system has an interlockswitch such that if a vacuum is called for and not achieved, thecontrols will prevent the stylus from going down and the servos fromoperating.

The control apparatus, referred to, includes a manually operable feedrate control 390, shown on the control panel. The feed rate controldetermines the speed at which the stylus moves over the material to bemarked and proportions the speed between the A and B assemblies inaccordance with information received from the tape.

From the foregoing description of the preferred embodiment of theinvention and alternate constructions mentioned, it will be apparentthat the objects of the invention heretofore enumerated and others havebeen accomplished. While the preferred embodiment of the invention hasbeen described in considerable detail, it is to be understood thatalternative constructions and arrangements may be employed, for example,screws, tapes, etc., could be substituted for the racks shown, theapertures in the turret head for supporting the styli, which are showncylindrical, could be any other suitable shape, etc., and theinformation source could be absolute as Well as incremental digital dataand the servo control may utilize absolute as well as incrementalinformation, etc.

It is the intention to hereby cover all embodiments of the inventionwhich come within the practice of those skilled in the art to which itrelates and the appended claims.

Having described our invention, we claim:

1. In a drafting machine: a table for supporting an article to bemarked; first and second beams; means attaching said beams to said tablein parallel spaced relation to one another; a first movable assemblyextending between and carried by said first and second beams; first andsecond individual digitally controlled signal responsive motor means onopposite ends of said assembly responsive for moving said first assemblyback and forth on said beams; a second movable assembly on said firstmovable assembly, third individual digitally controlled signalresponsive motor means on said second assembly for moving said secondassembly back and forth on said first assembly; stylus means on saidsecond movable assembly for marking an article supported on said table;and electronic control means for controlling the energization of saidmotor means whereby said stylus means is caused to traverse the articlesupported on said table in a predetermined manner, said control meanscomprising an input source of digital pulse information, a table sourceof digital pulse information, pulse separator means for combiningdigital pulses from said sources of information and for time-separatingsaid pulses, and circuit means for interconnecting said sources of pulseinformation, said pulse separator means and said motor means.

2. In a drafting machine: a table for supporting an article to bemarked; first and second beams, means at taching said beams to saidtable in parallel spaced relation to one another; first and second rackmeans attached to said first and second beams, respectively, andextending lengthwise therealong; a first movable assembly extendingbetween and carried by said first and second beams; first and secondindividual signal responsive motor means on opposite ends of saidassembly responsive for moving said first assembly back and forth onsaid beams; said first movable assembly including a third beam extendingbetween said first and second beams; a third rack means connected tosaid third beam and extending lengthwise therealong; a second movableassembly on said first movable assembly, third individual signalresponsive motor means on said second assembly for moving said secondassembly back and forth on said first assembly; said first, second andthird signal responsive motor means on said first and second movableassemblies geared to said first, second and third rack means,respectively, for moving said assemblies; stylus means mounted on saidsecond movable assembly for marking an article supported on said table;solenoid means for controlling movement of said stylus means into andout of contact with the article to be marked supported on said table;and electronic control means including an input source of incrementalpulses for controlling energization of said first, second, and thirdmotor means, and for controlling energization of said solenoid means formoving said stylus means into and out of contact with an article to bemarked supported on said table, said control means further includingdigital means for sensing the movement of said movable assemblies andproviding incremental pulses representative of such movement; andelectronic means operatively connected to said input source and saiddigital means for combining in timed relationship said incrementalpulses from said input source with said incremental pulses from saiddigital means to thereby controllably energize said motor means.

3. In a drafting machine: a table for supporting an article to bemarked; first and second beams, means attaching said beams to said tablein parallel spaced relation to one another; first and second rack meansattached to said first and second beams, respectively, and extendinglengthwise therealong; a first movable assembly extending between andcarried by said first and second beams; first and second individualsignal responsive motor means on opposite ends of said assemblyresponsive for moving said first assembly back and forth on said beams;said first movable assembly including a third beam extending betweensaid first and second beams; a third rack means connected to said thirdbeam and extending lengthwise therealong; a second movable assembly 17on said first movable assembly, third individual signal responsive motormeans on said second assembly for moving said second assembly back andforth on said first assembly; said first, second and third signalresponsive motor means on said first and second movable assembliesgeared to said first, second and third rack means, respectively, formoving said assemblies; synchro means operatively connected to oppositeends of said first movable assembly for coordinating the movement ofsaid ends with one another; stylus means mounted on said second movableassembly for marking an article supported on said table; solenoid meansfor controlling movement of said stylus means into and out of contactwith the article to be marked supported on said table; and electroniccontrol means including an input source of incremental pulses forcontrolling energization of said first, second, and third motor means,and for controlling energization of said solenoid means for moving saidstylus means into and out of contact with an article to be markedsupported on said table, said control means further including digitalmeans for sensing the movement of said movable assemblies and providingincremental pulses representative of such movement; and electronic meansoperatively connected to said input source and said digital means forcombining in timed relationship said incremental pulses from said inputsource with said incremental pulses from said digital means to therebycontrollably energize said motor means.

4. In a drafting machine: a table for supporting an article to bemarked; first and second beams, means attaching said beams to said tablein parallel spaced relation to one another; first and second carriageson said first and second beams, respectively, and movable back and forththereon; a third beam connected to said first and second carriages andforming therewith a first movable assembly; a third carriage on saidthird beam, movable back and forth thereon and forming a second movableassembly; first motive power means for moving said first movableassembly; second motive power means for moving said second assembly;means on said third carriage compensating for dilferences in weightbetween said first movable assembly and said second movable assemblywhereby the moments of inertia of said movable assemblies areapproximately the same; stylus means mounted on said second movableassembly for marking an article supported on said table; solenoid meansfor controlling movement of said stylus means into and out of contactwith the article to be marked supported on said table; and meansincluding a source of incremental pulses for controlling energization ofsaid first motive power means, another source of incremental pulses forcontrolling energization of said second motive power means, and a thirdsource of pulses for controlling energization of said solenoid means formoving said stylus means into and out of contact with an article to bemarked supported on said table.

5. In a drafting machine: a table for supporting an article to bemarked; first and second beams, means attaching said beams to said tablein parallel spaced relation to one another; first and second rack meansattached to said first and second beams, respectively, and extendinglengthwise therealong; first and second carriages on said first andsecond beams, respectively, and movable back and forth thereon; a thirdbeam connected to said first and second carriages and forming therewitha first movable assembly; a third rack means connected to said thirdbeam and extending lengthwise therealong; a third carriage on said thirdbeam, movable back and forth thereon and forming a second movableassembly; first, second and third motive power means on said first,second and third carriages geared to said first, second and third rackmeans, respectively, for moving said assemblies; means on said thirdcarriage including a flywheel geared to said third rack compensating fordifferences in weight between said first movable assembly and saidsecond movable assembly whereby the moments of inertia of said movableassemblies are approximately the same;

stylus means mounted on said second movable assembly for marking anarticle supported on said table; solenoid means for controlling movementof said stylus means into and out of contact with the article to bemarked supported on said table; and means including a source ofincremental pulses for controlling energization of said first and secondmotive power means, another source of incremental pulses for controllingenergization of said third motive power means, and a third source ofpulses for controlling energization of said solenoid means for movingsaid stylus means into and out of cont-act with an article to be markedsupported on said table.

6. In a drafting machine: a table for supporting an article to bemarked; first and second beams, means attaching said beams to said tablein parallel spaced relation to one another; first and second rack meansattached to said first and second beams, respectively, and extendinglengthwise therealong; first and second carriages on said first andsecond beams, respectively, and movable back and forth thereon; a thirdbeam connected to said first and second carriages and forming therewitha first movable assembly; a third rack means connected to said thirdbeam and extending lengthwise therealong; a third carriage on said thirdbeam, movable back and forth thereon and forming a second movableassembly; first, second and third motive power means on said first,second and third carriages geared to said first, second and third rackmeans, respectively, for moving said assemblies; an indexible stylusturret on said second movable assembly; first solenoid means forindexing said stylus turret; styli means mounted in said indexiblestylus turret for marking an article supported on said table and adaptedto be sequentially located in an operating station upon indexing of saidstylus turret; means including a source of incremental pulses forcontrolling energization of said first and second motive power means,another source of incremental pulses for controlling energization ofsaid third motive power means, a third source of pulses for controllingenergization of said first solenoid means for indexing said stylusturret and a fourth source of pulses for controlling energization ofsaid second solenoid means for controlling movement of a stylus means insaid operating station into and out of contact with an article to bemarked supported on said table.

7. In a drafting machine: a table for supporting an article to bemarked, first and second beams, means attaching said beams to said tablein parallel spaced relation to one another, first and second rack meansattached to said first and second beams, respectively, and extendinglengthwise therealong; first and second carriages on said first andsecond beams, respectively, and movable back and forth thereon; a thirdbeam connected to said first and second carriages and forming therewitha first movable assembly; a third rack means connected to said thirdbeam and extending lengthwise therealong, a third carriage on said thirdbeam movable back and forth thereon and forming a second movableassembly; first, second and third motive power means on said first,second and third carriages geared to said first, second and third rackmeans, respectively, for moving said assemblies; synchro meansoperatively connected to said first and second carriages forcoordinating their movement with one another; means on said thirdcarriage including a flywheel geared to said third rack compensating fordifferences in weight between said first and second movable assemblieswhereby the moments of inertia of said movable assemblies areapproximately the same; an indexible stylus turret on said thirdcarriage; first solenoid means for indexing said stylus turret; stylimeans mounted in and indexible stylus turret for marking an articlesupported on said table and adapted to be sequentially located in anoperating station upon indexing of said stylus turret; second solenoidmeans for controlling movement of a stylus means in said operatingstation into and out of contact with the article to be marked supportedon said table; and means including a 19 numerical control continuouspath or contouring director and cooperating digital transducers on eachof said movable assemblies for controlling energization of said first,second and third motive power means on said carriages and energizationof said second solenoid means for moving said stylus means into contactwith the article to be marked supported on said table.

8. In a drafting machine: a table for supporting an article to bemarked; first and second tubular beams, each of said beams having atleast one planar side with at least one V way on said planar side; meansattaching said beams to said table in parallel spaced relation to oneanother with said planar sides normal to the plane of said table; afirst movable assembly extending between and carried by said first andsecond beams; first and second independent signal responsive motor meanson opposite ends of said assembly responsive for moving said firstassembly back and forth on said beams; said first movable assemblyincluding a third tubular beam, having at least one planar side with atleast one V way on said planar side, said planar side being normal tothe plane of said table, extending between said first and second beams;an internal web in each of said beams extending from one side thereof tosaid planar side parallel to the plane of said table; a second movableassembly on said third beam movable back and forth thereon; and adrafting instrumentality connected to said second movable assembly.

9. In a drafting machine: a table for supporting an article to bemarked; first and second tubular beams, each of said beams having atleast one planar side with at least one V way on said planar side; meansattaching said beams to said table in parallel spaced relation to oneanother; a first movable assembly extending between and carried by saidfirst and second beams; first and second individual signal responsivemotor means on opposite ends of said assembly responsive for moving saidfirst assembly back and forth on said beams; said first movable assemblyincluding a third tubular beam extending between said first and secondbeams, having at least one planar side with at least one V way on saidplanar side, said planar side being normal to the plane of said table,extending between said first and second beams; an internal web in eachof said beams extending from one side thereof to said planar sideparallel to the plane of said table; a second movable assembly on saidfirst movable assembly, third individiual signal responsive motor meanson said second assembly for moving said second assembly back and forthon said first assembly; a plurality of electrical conductors on theunderside of each of said beams; means insulating said conductors fromsaid beams; a projection on each of said movable assemblies extendingunderneath the said beam along which it travels; a plurality ofresilient current collectors carried by each of said projections and insliding contact with one of said electrical conductors; and a draftinginstrumentality connected to said second movable assembly.

10. In a stylus head for a drafting or like marking apparatus: a frame;a turret body rotatably supported in said frame and having a pluralityof apertures therethrough parallel with the axis of rotation thereof andsymmetrically spaced about said axis of rotation; each of said aperturesbeing adapted to receive a discrete stylus assembly; means for indexingsaid turret body whereby styli carried thereby are sequentially indexedthrough a working station; means for moving a stylus in said workingstation into engagement with work to be marked; said index meanscomprising a plurality of ratchet teeth on said turret body; a bellcrank lever having two arms and pivotally connected to said frame formovement about an axis parallel with the axis of rotation of said turretbody and spaced therefrom; an indexing pawl pivotally connected to onearm of said bell crank level and adapted to cooperate with said ratchetteeth to index said turret body upon oscillation of said bell cranklever; an abutment on said turret body adjacent to each of saidapertures therein;

said other arm of said bell crank lever having an abutment adapted tosequentially engage one of said abutments on said turret body; and meansfor holding said abutments on said turret body in engagement with saidabutment on said other arm of said bell crank lever.

11. In a stylus head for a drafting or like marking ap' paratus: aframe; a turret body rotatably supported in said frame and having aplurality of cylindrical apertures therethrough parallel with the axisof rotation thereof and symmetrically spaced about said axis ofrotation; each of said apertures being adapted to receive a discretestylus assembly; means for indexing said turret body whereby stylicarried thereby are sequentially indexed through a working station;means for moving a stylus in said working station into engagement withWork to be marked; said index means comprising a plurality of ratchetteeth on said turret body; a bell crank lever having two arms andpivotally connected to said frame for movement about an axis parallelwith the axis of rotation of said turret body and spaced therefrom; anindexing pa'wl pivotally connected to one arm of said bell crank leverand adapted to cooperate with said ratchet teeth to index said turretbody upon oscillation of said bell crank lever; an abutment on saidturret body adjacent to each of said apertures therein; said other armof said bell crank lever having an abutment adapted to sequentiallyengage one of said abutments on said turret body; and means for holdingsaid abutments on said turret body in engagement with said abutment onsaid other arm of said bell crank lever.

12. In a stylus head for a drafting or like marking apparatus: a frame;a turret body rotatably supported in said frame and having a pluralityof apertures therethrough parallel with the axis of rotation thereof andsymmetrically spaced about said axis of rotation; each of said aperturesbeing adapted to receive a discrete stylus assembly; spring meansinterposed between said turret body and a stylus in any of saidapertures; means for indexing said turret body whereby styli carriedthereby are sequentially indexed through a working station; means formoving a stylus in said working station against the bias of said springinterposed therebetween and said turret body; said index meanscomprising a plurality of ratchet teeth on said turret body; a bellcrank lever having two arms and pivotally connected to said frame formovement about an axis parallel with the axis of rotation of said turretbody and spaced therefrom; an indexing pawl pivotally connected to onearm of said bell crank lever and adapted to cooperate with said ratchetteeth to index said turret body upon oscillation of said bell cranklever; an abutment on said turret body adjacent to each of saidapertures therein; said other arm of said bell crank lever having anabutment adapted to sequentially engage one of said abutments on saidturret body; and means for holding said abutments on said turret body inengagement ivith said abutment on said other arm of said bell crankever.

13. A stylus adapted to be supported in a movable supporting structurehaving one ormore stylus receiving apertures therein and yieldable meansfor engaging the stylus: a cylindrical tubular body member adapted to beslidably supported in a stylus receiving aperture of a supportingstructure; a second member at one end of said stylus body memberslidably connected thereto for movement lengthwise of said body member;resilient means interposed between said members; means for limitingmovement of said members in a direction away from one another underaction of said resilient means; and a marking instrumentality secured tothe end of said stylus body member other than the end at which saidsecond member is located.

14. A stylus adapted to be supported in a movable supporting structureof a drafting machine and having one or more stylus receiving aperturestherein and resilient means for engaging the stylus when moved thereinin one direction; a cylindrical tubular body member adapted to beslidably supported in a stylus receiving aperture of a

1. IN A DRAFTING MACHINE: A TABLE FOR SUPPORTING AN ARTICLE TO BEMARKED; FIRST AND SECOND BEAMS; MEANS ATTACHING SAID BEAMS TO SAID TABLEIN PARALLEL SPACED RELATION TO ONE ANOTHER; A FIRST MOVABLE ASSEMBLYEXTENDING BETWEEN AND CARRIED BY SAID FIRST AND SECOND BEAMS; FIRST ANDSECOND INDIVIDUAL DIGITALLY CONTROLLED SIGNAL RESPONSIVE MOTOR MEANS ONOPPOSITE ENDS OF SAID ASSEMBLY RESPONSIVE FOR MOVING SAID FIRST ASSEMBLYBACK AND FORTH ON SAID BEAMS; A SECOND MOVABLE ASSEMBLY ON SAID FIRSTMOVABLE ASSEMBLY, THIRD INDIVIDUAL DIGITALLY CONTROLLED SIGNALRESPONSIVE MOTOR MEANS ON SAID SECOND ASSEMBLY FOR MOVING SAID SECONDASSEMBLY BACK AND FORTH ON SAID FIRST ASSEMBLY; STYLUS MEANS ON SAIDSECOND MOVABLE ASSEMBLY FOR